Rotary diamond dressing tool



Jan- 27., 1970 y A. T. KoHlfsTf-mrm 3,491,740

ROTARY DIAMOND DRESSING 'rooL v l Filed Marh v, 1967 INVENTOR.

lz 2512 f5 fwzfffgfw BY v ATTORNEYS United States Patent U.S. Cl. 125--11 3 Claims ABSTRACT 0F THE DISCLOSURE A free-wheeling rotary dressing wheel formed from a sealed radial bearing assembly by electrodepositing an annular band of metal-imbedded abrasive particles, such as diamond particles, as a layer on the outer bearing race. The assembly prior to the electrodeposition step is protected by an electrically non-conductive covering thereover enclosing all except the area representing said annular band, and the protected assembly is then immersed in an electrolytic bath for depositing, first, a flash metal coating over said band then, during the continued electrodepositing of metal, applying the abrasive particles to the metal layer as it is built up in thickness and thereby form a layer of metal-imbedded abrasive particles on the working face of the resulting rotary dressing Wheel.

This invention relates to a rotary abrasive dressing wheel assembly. More particularly, the dressing wheel assembly comprises a sealed radial bearing assembly provided with a relatively narrow band about the outer race of the assembly that is formed of a layer of metal-imbed-ded abrasive particles, such as fine diamond particles.

The rotary diamond dressing wheel assembly of my invention is particularly adapted for use in the dressing of grinding wheels. In such use, the assembly is mounted in free-wheeling surface contact with the working face of the grinding wheel and the axis of the assembly is at an angle other than a right angle to the plane of revolution of "the grinding wheel to thereby ensure a difference in surface speeds between the contacting surfaces of the dressing wheel and of the grinding wheel.

By starting with a standard, sealed radial bearing assembly, having either ball, roller or needle, radial bearing elements, such assembly can readily be converted into my free-wheeling rotary dressing assembly by the following method. Such method involves covering with a dielectric enclosure all surfaces of the bearing assembly except a relatively narrow band along the outer annular surface of the outer bearing racerand then applying to said narrow band an electrodeposited composite layer of metal and abrasive particles, specifically diamond particles, the particles being embedded in and firmly held by the electrodeposited metal. In the plating bath, a metal, such as nickel, is preferably deposited as a flash coating over the exposed surface of the band. During continued plating out of nickel, diamond particles are deposited onto the nickel coating to become embedded therein and firmly held thereby. Since the sealed bearing assembly is provided with a covering of electrically non-conductive material completely enclosing the assembly except for the band to be plated, upon immersion of the assembly inan electrolytic plating bath, only the band itself is exposed to the electrolyte of the plating bath to receive the sequential electrodeposits of nickel and the periodic applications thereto of diamond particles while a suitable electric current is caused to flow through the plating bath.

It is therefore an important object of this invention to provide a relatively inexpensive device which converts a standard, sealed radial bearing assembly into a rotary abrasive dressing wheel for the dressing of grinding wheels.

3,491,740 Patented Jan. 27, 1970 ice Other objects and advantages of my invention will become apparent from the following description of the drawings, in which like reference numerals are used to designate like parts and in which:

FIG. l is a vertical sectional view of a standard, sealed radial bearing assembly suitably enclosed by electrically non-conductive materials except for the narrow annular band on the outer race of the bearing assembly that is to be plated, with the assembly immersed within a bath of an electrolyte as a part of the plating circuit;

FIG. 2 is a perspective view of the finished rotary abrasive dressing wheel in assembled form, and

FIG. 3 is an enlarged sectional view taken substantially along the line III-III of FIG. 2, with parts broken away and in section. As shown on the drawings:

ln FIG. 1 there is illustrated more or less diagrammatically a plating tank 10 containing a bath 11 of suitable electrolyte, the upper surface, or level, of the bath being indicated by the reference numeral 12. A standard, sealed radial bearing assembly indicated generally by the reference numeral 13, is disposed within said bath 11 after being first partially enclosed by electrically nonconductive materials in a manner that will be more fully described later on herein.

Said bearing assembly 13 mounted on a temporary stub shaft 14, comprises an inner bearing race 15 received upon the smooth cylindrical portion 27 of said shaft; an outer bearing race 16 mounted in spaced relation to said inner bearing race 15 with an annular space 17 therebetween; steel balls 18 within said space 17 and in bearing contact with annular inner and outer grooves 19 and 20, respectively, of said inner and outer bearing races; and two-part annular sealing means 21 between and secured to the inner and outer bearing races 15 and 16 so as to completely seal the annular space 17 and the steel balls 18. Since the sealed bearing assembly 13 is of a wellknown design, construction and arrangement, any further description thereof would appear to be unnecessary.

As is usual, all parts of the bearing assembly 13 are of metal with the possible exception of the sealing means 21, which may be of metal, plastic material, or metal coated with a plastic material that is inert to moisture and greases. The annular space 17, as is customary, is filled, or partially filled, with lubricating material (not shown) so as to provide lifetime lubrication for the bearing elements. The ends of the temporary mounting shaft 14 are externally threaded as at 22 and 23 for a purpose that will later appear.

Prior to immersing the sealed bearing assembly 13 within the tank 10, the assembly is provided with means partially enclosing the same so as to limit the surface exposed to the electrolyte 11 to a relatively narrow, annular, band-like portion 24 on said outer bearing race 16 symmetrically arranged with respect to the median thereof but terminating short of the peripheral edges thereof. Said enclosing means includes a lower jig 25, which may be of molded dielectric material, such as a synthetic organic plastic, in the form of a relatively thick cylindrical block having an axially extending bore 26` therethrough. Said bore is of such dimensions as to freely receive the smoothly cylindrical portion 27 of the shaft 14, with the jig 2S held in position on said shaft by means of a nut 28 threaded upon the lower threaded end 23 of the shaft against the bottom surface 29 of said jig.

The jig 25 is provided on its upper surface 30 with an annular trough 31 having a sloping radially outer surface 32 and a flat annular surface 33 forming the bottom of said trough and opening radially inwardly. Stepped counterbores 34 and 35 are formed radially inwardly of the trough 31 and extend axially beyond the bottom 33 of said trough to provide radial extending annular wall surfaces 36 and 37, respectively. There are thus formed a lower annular groove 39 for the reception of the lower end of the inner race and of the lower part of the sealing means 21, and a shallower groove 40 axially upwardly of the groove 39 for receiving the lower portion of the outer bearing race 16.

Said outer bearing race 16, when in position in the groove 40, forms the radially inwardly end Wall, as at 41, for the otherwise open inner end of the trough 33. Between the lower surface of the outer bearing race 16 and the bottom surface of the groove 40, there is positioned a sealing washer 42, preferably of neoprene, and between the lower end surface of the inner race 15 and the bottom surface of the groove 37 is positioned a similar sealing washer 43, both of which washers serve as additional sealing means to prevent any of the electrolyte 11 from seeping from the trough 31 into contact with the shaft 14.

A cooperating upper jig, indicated generally by the reference numeral 45, provides much the same protection for the upper portion of the sealed bearing assembly 13 as the jig 25 does for the lower portion of said assembly. Said upper jig 45, like the jig 25, is formed of suitable dielectric material and is provided with an axial bore 46 through which the upper threaded end 22 of the shaft 14 freely extends, with the smoothly cylindrical portion 27 of said shaft received therein. Said upper jig 45 is formed with an outer integral, downwardly directed cylindrical flange portion 47, provided at its lower end with an annular, inner groove 48 for receiving the upper end of the outer bearing face 16. A sealing washer 49, formed of neoprene or other similar oil and moisture resistant plastic material, is positioned between the upper end face of said outer bearing race 16 and the radially extending surface of the groove 48 to provide an impervious seal therebetween. The upper portion of the sealing means 21 extends into the annular space 50 between the inner, axially extending, cylindrical wall of the flange 47 and the upper part of the sealing means 21. A sealing washer 51 is positioned between the upper end face of the inner bearing race 15 and the lower surface of the planar wall of the upper jig 45. This washer 51 serves the same sealing purpose as the other washers 49, 42, and 43.

A nut 52 is threaded onto the upper threaded end 22 of the shaft 14 to rest firmly against the upper surface 53 of the upper jig 45. With the upper and lower jigs 45 and 25, and the upper and lower nuts 52 and 28 threaded into position, as described, and with the nuts 52 and 28 tightened up on the respective threaded ends 22 and 23 of the shaft 14, insulating coatings of a liquid plastic, or other electrically non-conductive material, indicated by the reference numerals 54 and 55, are applied and allowed to harden over said nuts 52 and 28, respectively, to prevent the metal of the nuts and of the shaft 14 from contact with the electrolyte 11 of the plating tank 10. Additionally, the coating 54 is continued radially inwardly, as at 56 over the upper threaded end 22 of the shaft to lie against an axially concentric, cylindrical stem 57 that projects from said threaded end 22 to a point above the level 12 of the bath of electrolyte 11. Said stem 57 need not be an integral portion of the shaft 14, but must be in metal-to-metal contact with the upper end of such shaft, as by being soldered or lightly brazed thereagainst, so as to be in an electrically conductive relationship therewith.

In order to make the metal portion of the sealed bearing assembly 13 a part of the electrical circuit that includes the electrolyte 11, a clamp 60 is attached to the upper end of the stem 57, and said clamp is, in turn, connected through an electrical lead 63 with the positive (-1-) side 62 of a suitable source (not shown) of direct current. Electrodes 64 are positioned in the bath of electrolyte 11 on either side of the bearing assembly to provide electrodes of opposite polarity to that of the metal parts of the bearing assembly 13, and said electrodes 64 are connected through leads 65 to the negative side 66 of the same source of electrical power. The lead 65 should, of course, be insulated, as indicated by the reference numeral 67, from the action of the electrolyte 11.

With the bearing assembly enclosed and immersed, all as indicated in FIG. 1, the open trough 31 becomes lilled with the electrolyte so that the electrolyte is in direct contact with the exposed surface 24 of the outer bearing race 16. Said surface is in the form of a narrow cylindrical band of a width, or height, that is typically about M; of an inch and that is symmetrical about the median plane of said race at right angles to the axis of the shaft 14.

In carrying out my method of applying diamonds to the surface of the exposed band 24, it is preferable first to apply a flash coating of nickel to said surface, as indicated by the reference numeral 70 (FIG. 3). Such nickel flash coating, which may be about 0.0002 inches in thickness, is confined to the band 24 and provides a base, or cushion layer, for the subsequently applied diamond particles.

Either after or prior to the application of said flash nickel coating, diamond particles, indicated by the reference numeral 71, are placed in the trough 33 to substantially fill the trough. This supply of diamond particles is suflicient to form a relatively thin composite layer 72 of electrodeposited nickel and of diamond particles over the surface of the nickel flash coating (FIG. 3).

The diamond particles are generally of such a fine particle size that between 1000 and 5000 particles are required to make up 1 carat.

The diamonds in the composite layer 72 preferably constitute a single layer of diamond particles. The composite layer 72 is, in general, approximately 0.010 inch, in thickness.

A more detailed description of the process of forming the composite metal-diamond layer 72 will be given hereinafter.

After the method has been carried out, the enclosed sealed bearing assembly, now converted into a rotary diamond dressing wheel sub-assembly 80, is removed from its associated protective enclosure. For this purpose, the insulating coatings 54 and 55 are irst stripped away and the nuts 52 and 28 threaded olf of the threaded ends 22 and 23 of the shaft 14. With the nuts removed, the upper and lower jigs 45 and 25 are pulled off of the shaft 14 over the respective ends 22 and 23 of the shaft 14 and the sealing discs 51, 49, 42 and 43 are removed from the ends of the bearing races, or caused to drop off the same. v

.The converted sealed bearing assembly 13, with the diamond impregnated layer 72 in place on the outer bearing race 16, is then removed from shaft 14, and the resulting rotary dressing wheel sub-assembly is mounted in a holder, indicated generally by the reference numeral 75 (FIGURE 2), said holder includes a U- shaped member 76 having integral spaced plates 77 and 78 as legs of said U-shaped holder 75. The ends of a bearing support pin 7'9 are adapted to be rmly secured 1n said plates 77 and 78. The finished bearing sub-assembly 80 is mounted in properly centered, lixed relation on the bearing support pin 79, in equi-spaced relation to the mner surfaces of said plates 77 and 78, so as to be freewheeling about the bearing support pin, or shaft 79, by virtue of the steel balls 18 and the associated inner and outer bearing races 15 and 16. The holder 75 is provided with an integral cylindrical boss or stub shaft 81 for supporting the holder 75 in the desired position on an arbor, or the like, (not shown), when the rotary diamond dressing wheel assembly now indicated as a whole by the reference numeral 82, is used for the dressing or trueing of a grinding wheel.

When in use, as earlier stated herein, the diamond rotary dressing wheel 80 is so positioned with respect to the grinding wheel to be dressed that the axis of the rotary dressing wheel is at an angle other than 90 to the plane of revolution of the grinding wheel. When so positioned, with the surface of the diamond plated annular layer 72 in contact with the working face of the grinding wheel, the diamond rotary dressing wheel, being freely rotatable about its bearing support pin 79, rotates with the grinding wheel but with a differential surface speed therebetween because of the angular relationship between the axis of the bearing support pin 79 and the plane of revolution of the grinding wheel, and, hence, causes an effective dressing or trueing of the working face of the grinding wheel.

With further reference to the process of forming the composite layer 72 of diamonds embedded in nickel, the electrodeposition of the nickel can best be carried out in a sulfamate nickel plating bath, although other known nickel plating baths, such as the Watts bath can be used. The sulfamate nickel plating bath gives a harder and brighter nickel than a Watts bath.

The sulfamate bath suitably comprises a conventional sulfamate nickel plating solution, such as available from Allied Chemical Corporation, containing about 4 ounces per gallon of boric acid, having a density of about 30" Be. and a pH of between 3.5 and 5.0. The temperature of the bath is preferably maintained at about 120 F., or, more broadly, between about 110 and 140 F., during operation of the bath. Rolled depolarized nickel anodes are preferably used as the electrodes 64. A pump 90, having an inlet 91 near the bottom of the vessel 10, serves to circulate the electrolyte through piping 92 to an inlet connection 93 positioned near the top and at the other side of said tank. The pump maintains a continuous circulation of the bath during plating. A heater (not shown) maintains the bath at the preferred temperature of 120 F.

The surface of the band 24 to be plated is prepared for plating in any conventional way, as by anodic cleaning in a hot alkaline cleaner, followed by rinsing and an acid pickle. The sealing bearing assembly is then ready for immersion in the tank 10.

The current used in plating is preferably 120 milli amps. per square inch, suicent to deposit a nickel plate of 0.001 inch thickness per square inch of deposit.

After flash coating for 30 minutes, the diamond particles 71 are dropped into the trough 31 to substantially ll the same all around its circular extent. Plating of nickel is continued at about 35 milli-amps. for four hours. During two hours of this length of time, and at about 20 minute intervals, the diamond particles are pushed gently against the surface receiving the nickel plate, using a spatula or similar instrument to effect the application of the diamonds to the nickel plated surface. The diamonds are spread as uniformly as possible over the surface so as to give a layer of diamonds of a single diamond thickness.

In order to get a uniform thickness of nickel plate, the jig-assembled bearing unit is turned periodically during the plating operation, usually each hour. At the end of about four hours from the start of the 35 milli-amp. current, the diamonds remaining in the trough 31 are removed therefrom, as by use of a syringe, and the current increased to .milli-amps. for 21/2 more hours.

At the end of the operation the composite layer 72 comprises a continuous matrix of nickel 70 with diamond particles 71 embedded therein as a single layer of particles with the points 73 thereof exposed, Such exposure of the points is due to the fact that the nickel does not plate onto the diamond surfaces themselves, but only upon already deposited nickel. The extent of the deposition of nickel is such as ll up the valleys between the diamond particles but to leave the points exposed.

Other metals than nickel can be used, such as those that are not easily oxidized, e.g., cobalt and the nobler metals, but nickel is preferred.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim:

1. In a rotary abrasive dressing tool including a sealed bearing assembly having a shaft, inner and outer bearing races with an annular Space therebetween, bearing elements in said space between said race and means completely sealing said space and said bearing elements therein, the improvement which comprises the provision on the outer surface of said outer bearing race of a layer of embedded abrasive particles secured to and projecting from said outer surface,

said layer being confined to a narrow band including the median line of said outer bearing race and terminating short of the peripheral edges of said bearing race.

2. A dressing tool as defined by claim 1, wherein,

said abrasive particles are diamond particles, and

said particles are embedded in yan electrodeposit of metal of about 0.010 inch in thickness.

3. A dressing tool as defined by claim 2, wherein,

said metal is nickel, and

said diamond particles have points thereof protruding from the nickel.

References Cited UNITED STATES PATENTS 2,034,507 3 1936 Colson 51--291X 2,495,492 l/ 1950 Wilson -11 2,809,474 10/ 1957 Newman 12S-11X FOREIGN PATENTS 499,285 6/ 1930 Germany. 1,125,805 3/1962 Germany.

HAROLD D. WHITEHEAD, Primary Examiner US. Cl. X.R. 51-206 

